Embodiments of the invention relate to transmission lines and, more particularly, to reducing the amount of conductive material in transmission lines used in high-frequency (RF) applications.
It is well know that as the frequency of an electrical signal increases, the RF (radio frequency) energies tend to concentrate near the surface or skin of the conductor medium. The higher the frequency, the thinner the conduction layer under the conductor surface. There are techniques employed to mitigate this phenomena such as using stranded wire instead of a solid conductor to increase the effective surface area of the conductor.
This phenomena is caused by the self-inductance of the conductor. All alternating current flow has associated therewith electrical fields and corresponding magnetic fields that influence the carriers (electrons) and tend to force them to the surface of the conductor. The higher the frequency, the greater the force towards the surface. This is most pronounced in RF applications. This phenomena causes increased effective resistance of a conductor for alternating currents (AC) at higher frequencies as compared with the resistance of the same conductor with a direct current (DC) or a current of lower AC frequencies.
For these reasons, among others, simple interconnections between electronic devices operating in high frequency ranges (i.e., giga-hertz) cannot be effectively used. Instead, signals are carried via waveguide devices such as coplanar waveguides or micro strip devices. In the case of coplanar waveguides, parallel conducting lines patterned on a dielectric surface are used to carry signals. However, just as described above, at high frequencies current tends to move along the surface of the conductors. In addition, due to the geometries of the parallel conducting lines, current tends to concentrate along adjacent edges of the conductors. This is sometimes referred to as the xe2x80x9cedge effectxe2x80x9d.